I reload at the earliest opportunity when I know it is safe (run back a bit and reload, then advance) - I usually encounter multiple groups of people so I try to keep my gun ready to take on 2-4 enemies. If I see four, I will immediately switch to nades, then get my gun out and kill who I deem the most threatening to my life. If I see two, I will one-two them usually aiming for whoever is a closer threat.
As I advance my assault, I usually start with grenades on common areas of high traffic, and I will throw a single bag in front of me and get my gun out. This allows me to reload all four nades quickly, but still have my gun out to defend as I run over my own bag. Even if I don't get any nade kills, If I see a crosshair flare I know someone is there and semi-injured.
I play Sharqi for infantry, so the combat is usually intense and it is a sure bet to see more then one guy in one go. I use the RPK not only for it's excellence in killing, but because its clip size and overheat time let me take out multiple enemies. If I am medic I take the G36E for mid to long range flags, and the Ak101 for close range flags where I will be fighting CQC. Medic seems to have trouble killing more then three infantry in one clip, so I will reload as early as possible with it so I don't get stuck in a firefight with no bullets left - whereas I let the RPK run down to about 40 bullets before reloading.
I will occasionally take the PKM for longer range flags or if a helicopter is about. The PKM I reload after every set of kills though as it's clip size is a bit low.
If I need AT, I'll swap to it for one death and take the DAO12 and reload as early as possible. The DAO12 struggles with longer range kills and you need all the ammo in your clip available for multitarget fighting. I hate having like 5 shells in a shotgun, chunka chunka and no kills and bam your are hamburgler.
I tend to stay away from other kits - Assault the G3 should be 30 clip size to make it truly shine, but it's 20 makes it a bit of a hinderance then an advantage - you have to reload often whether you like it or not. For Spec ops, I always opt for the G36C because of its low recoil, however its low 25 damage makes me stay away from Spec ops unless I see a short-term need for c4. I reload less often with the G36C then I do with the G36E simply because the medic is tri-burst which chews through your ammo quickly.
Sniper I don't reload until empty and engineer I'll opt for the MP7 and reload after any kills I get - it is a semi-good and semi-weak submachine gun.
Anyways, my preference is always for the RPK simply because you don't need to reload in firefights as much so that you never get caught with your pants down - others will run out of ammo and you can keep on firing which is a huge advantage, nevermind that the gun kicks ass and you get armor with the kit.
My gun preferences and why:
http://forums.bf2s.com/viewtopic.php?pid=299669#p299669Here's some screens I caught in the heat of battle this month - sometimes I don't press fraps f11 fast enough lol:


















Does anyone see this on their game? It is always there for me next to hotel flag: